Two compounds are standing at the same temperature. compound "a" is evaporating more slowly than compound " b." according to the kinetic molecular theory, which assumption can be made? compound b has a greater average kinetic energy. compound a has a greater average kinetic energy. compound a may have a lower molecular weight. compound b may have a lower molecular weight.

I believe the answer is compound B may have a lower molecular weight compared to compound A. 
At the same temperature, lighter particles of a compound have a higher average speeds than do heavier particles of another compound. Thus, particles of compound B are lighter than those of compound A and thus they have a higher average speed, hence evaporating faster compared to compound A.